Connection timeout when validating vCenter Server in VMware Aria Operations

Products

• VMware vSphere ESXi
• VMware vCenter Server
• VMware Aria Operations (formerly vRealize Operations) 8.x

Issue/Introduction

In VMware Aria Operations, when you add a vCenter Server and click on test connection to validate it, it comes back with a connection timeout.

However, via ping, the vCenter Server is reachable from Aria Operations.

Environment

VMware Aria Operations

VMware vCenter Server

Cause

The environment and all parts of the software stack are configured for jumbo frames, however the underlay networking is configured to allow an MTU (maximum transmission unit) size of only 1500 bytes or less.

This is evidenced by attempting to ping with different packet sizes as follows:
root@vcenter01 [~]# ping ariaops
PING ariaops (#.#.#.#) 56(84) bytes of data.
64 bytes from #.#.#.#: icmp_seq=1 ttl=51 time=3.40 ms
64 bytes from #.#.#.#: icmp_seq=2 ttl=51 time=5.55 ms
64 bytes from #.#.#.#: icmp_seq=3 ttl=51 time=4.67 ms
^C
 - - - #.#.#.# ping statistics - - -
3 packets transmitted, 3 received, 0% packet loss, time 5ms rtt min/avg/max/mdev 3.396/4.540/5.550/0.884 ms 

root@vcenter01 [~]# ping -s 1453 ariaops
PING ariaops (#.#.#.#) 1453 (1481) bytes of data.
^C
 - - - #.#.#.#  ping statistics - - -
9 packets transmitted, 0 received, 100% packet loss, time 193ms
root@vcenter01 [~]#

As observed in the ping output above, the default ping size of 64 bytes is successful, but the larger one with 1453 bytes is unsuccessful.

(In the example above, the underlay physical networking was set to an MTU size of 1480 bytes.  A ping sent with a data size of 1453 bytes ends up at 1481 bytes after adding 8 bytes from the ICMP header and another 20 bytes from IP headers.  1453 + 8 + 20 = 1481 bytes.)

Resolution

Increase the MTU frame size in the underlay physical network to atleast 1600 bytes or higher.